Abstract

BACKGROUND:

Posttraumatic stress disorder (PTSD), an anxiety disorder that can develop after exposure to psychological trauma, impacts up to 20 % of soldiers returning from combat-related deployment. Advanced neuroimaging holds diagnostic and prognostic potential for furthering our understanding of its etiology. Previous imaging studies on combat-related PTSD have focused on selected structures, such as the hippocampi and cortex, but none conducted a comprehensive examination of both the cerebrum and cerebellum. The present study provides a complete analysis of cortical, subcortical, and cerebellar anatomy in a single cohort. Forty-seven magnetic resonance images (MRIs) were collected from 24 soldiers with PTSD and 23 Control soldiers. Each image was segmented into 78 cortical brain regions and 81,924 vertices using the corticometric iterative vertex based estimation of thickness algorithm, allowing for both a region-based and a vertex-based cortical analysis, respectively. Subcortical volumetric analyses of the hippocampi, cerebellum, thalamus, globus pallidus, caudate, putamen, and many sub-regions were conducted following their segmentation using Multiple Automatically Generated Templates Brain algorithm.

RESULTS:

Participants with PTSD were found to have reduced cortical thickness, primarily in the frontal and temporal lobes, with no preference for laterality. The region-based analyses further revealed localized thinning as well as thickening in several sub-regions. These results were accompanied by decreased volumes of the caudate and right hippocampus, as computed relative to total cerebral volume. Enlargement in several cerebellar lobules (relative to total cerebellar volume) was also observed in the PTSD group.

CONCLUSIONS:

These data highlight the distributed structural differences between soldiers with and without PTSD, and emphasize the diagnostic potential of high-resolution MRI.

Group differences in AAL-guided cortical thickness analysis. Bar plots of the mean and ±1 standard error for cortical thickness in the regions from T-statistic maps highlighting regions with significant group effects of cortical thickness (PTSD n = 23, Control n = 24), as analyzed with a vertex-based analysis. Cool colours on the anatomical images indicate a relative thinning in the cortex for PTSD compared with Controls. The bar graphs of selected voxels are plotted, and show significant thinning in the left inferior parietal gyrus (1), the left superior motor area (2), and the left superior temporal gyrus (3); Asterisk denotes significant differences using unpaired t-tests with FDR = 10 %

Group differences in the relative volume of subcortical structures for PTSD and control soldiers (bar graphs show mean and ±1 standard error). Structural colour maps: blue caudate, green thalamus, purple putamen, orange globus pallidus. Significant differences (denoted by asterisk) were found in the caudate, with decreased relative volume in the PTSD compared with Control group. No other basal ganglia structure was found to be significantly different between the groups. Vertical axis of graphs shows relative volume in %

Group differences in the relative volume of cerebellar structures for PTSD and control soldiers (bar graphs show mean and ±1 standard error). Division colour maps: dark blue Lobule 1–2, light blue lobule 4, blue lobule 6, green lobule 9, purple lobule 7b, pink lobule 8a, orange lobule 8b. Significant differences between the groups (denoted by asterisk) were observed in the relative volume of the cerebellum in a number of regions, with enlargement found in lobules 7b, 8a and 8b in the PTSD compared with the Control group. Vertical axis of the graphs show relative volume in %